Re: [PATCH 1/1] cat-file: quote-format name in error when using -z

From: Phillip Wood <phillip.wood123@gmail.com>
Date: Dec 11, 2022, 16:30 UTC
Message-ID: <ddae1940-f58f-e410-7606-d0bcf8d06cd3@dunelm.org.uk>
In-Reply-To: <xmqq5yekyvrh.fsf@gitster.g>

On 09/12/2022 23:58, Junio C Hamano wrote:

Show 24 quoted lines

> Phillip Wood <phillip.wood123@gmail.com> writes:
> 
>> Hi Toon
>>
>> On 09/12/2022 15:00, Toon Claes wrote:
>>> Since it's supported to have NUL-delimited input, introduced in
>>> db9d67f2e9 (builtin/cat-file.c: support NUL-delimited input with `-z`,
>>> 2022-07-22), it's possible to pass paths that contain newlines. This
>>> works great when the object is found, but when it's not, the input path
>>> is returned in the error message. Because this can contain newlines, the
>>> error message might get spread over multiple lines, making it harder to
>>> machine-parse this error message.
>>> With this change, the input is quote-formatted in the error message,
>>> if
>>> needed. This ensures the error message is always on a single line and
>>> makes parsing the error more straightforward.
>>
>> Thanks for working on this. I'd previously suggested NUL terminating
>> the output of "git cat-file -z" to avoid this problem [1] but quoting
>> the object name is a better solution.
> 
> Hmph.  My knee-jerk reaction was that it is utterly disgusting if we
> quote when we do NUL-terminated.  Is your "quoting is OK over NUL
> terminating" because "-z" applies only to the input?

Yes, if the object exists then delimiting the output with newlines is fine, it is only if the object is missing and its name contains a newline that there is a problem. It also makes adopting "-z" in existing scripts easier as there is no change required when parsing the output.

As "-z" was added in 2.38 there is also a pragmatic reason to prefer quoting over NUL terminated output as it allows us to fix this issue without changing the output delimiter of an existing option.

> If so, then I
> would agree that is OK, but shouldn't the quoting apply regardless
> of how the input is formulated?  Why do we call the cquote helper
> only under "-z"?

Without "-z" you cannot pass object names that contain newlines so not quoting the output does not cause a problem. We could start quoting the object name without "-z" but we'd be changing the output without a huge benefit.

Best Wishes

Phillip